Recently, surface emitting bodies have attracted attention, the surface emitting bodies being used as backlights for various kinds of displays, display boards such as signboards and emergency lights, light sources for lighting fixtures and the like, because the surface emitting bodies have many advantages such as having high brightness, high light emission efficiency, small thickness and light weight. Among the surface emitting bodies, an organic electroluminescence element (hereinafter also called an organic EL element), which employs an organic material and emits light by electric energy from an anode and a cathode, has particularly attracted attention because the organic EL element can emit light at a low voltage of several volts to several ten volts, is of a thin-film type completely-solid state element and can save space, for example.
In order to increase the efficiency of the organic EL element, it is necessary to increase light extraction efficiency. However, the organic EL element has a short distance of several ten nm between a light emitting layer and a metal electrode. Hence, waveguide loss of surface plasmon mode light is large, and accordingly the light extraction efficiency does not increase. The element taking a top emission type structure is considered as a method for reducing the waveguide loss of the surface plasmon mode light.
One of the problems of the top emission type organic EL element is damaging the organic layers in a process of forming a transparent conductive layer, which lowers the light emission efficiency, increases a voltage and shortens life of the element, for example. In particular, the above problem is conspicuous when a sputtering method having high productivity is used as the process of forming the transparent conductive layer. Thus, it is a great challenge to balance productivity with element characteristics of the top emission type organic EL element. As a technology for balancing the productivity with the element characteristics, there has been a technology for preventing damage to the organic layers in the process of forming the transparent conductive layer by providing a layer (hereinafter called a transparent protective layer) made of a metallophthalocyanine material such as copper phthalocyanine between the transparent conductive layer and the light emitting layer (see Patent Documents 1 and 2). However, because copper phthalocyanine, which has low transmittance, is used as the material of the transparent protective layer, the light emission efficiency decreases, which is a weakness of the technology.
As another technology, it has been examined to use a layer made of a titanium oxide, a vanadium oxide, a zirconium oxide or a lanthanum oxide deposited in an oxygen deficient state (see Patent Document 3). This is a technology for preventing oxidation damage to the organic layers by trapping oxygen radical, which is generated in the sputtering process of forming the transparent conductive layer, with the transparent protective layer by utilizing the fact that the above-mentioned metal oxides in the oxygen deficient state are unstable. Hence, it is effective in preventing oxidation damage to the organic layers in the sputtering process, but has the problem that the voltage increases by oxidation of the transparent protective layer. In particular, if, in view of productivity, discharge power for sputtering is increased so that a deposition rate for the transparent protective layer becomes higher, it is necessary to make the transparent protective layer thick enough to prevent damage to the organic layers. When the transparent protective layer is thick, the problem that the voltage increases by oxidation of the transparent protective layer in the sputtering process becomes bigger.